Hello, could someone explain to me what exactly MODEL matrix is? What
transformation it represents? How can I extract it?

For example it this article:
http://developer.nvidia.com/object/Projective_Texture_Mapping.html
author is saying:

"M is the model matrix (not to be confused with the OpenGL
MODELVIEW matrix)"

What he is talking about? What operations/functions in OpenGL API
creates/modify this MODEL matrix?

sorry for this noob question but I can't find clear definition of
it

Thank You

BlendMan wrote:
> Hello, could someone explain to me what exactly MODEL matrix is? What
> transformation it represents? How can I extract it?
> 
> For example it this article:
> http://developer.nvidia.com/object/Projective_Texture_Mapping.html
> author is saying:
> 
> "M is the model matrix (not to be confused with the OpenGL
> MODELVIEW matrix)"
> 
> What he is talking about? What operations/functions in OpenGL API
> creates/modify this MODEL matrix?

OpenGL does not separate the model and the view matrices -- they are combined into
the single model-view matrix.

model-view = view * model

--
Andy V

Andy V wrote:
> OpenGL does not separate the model and the view matrices -- they are 
> combined into
> the single model-view matrix

I know that. I'm just curious what model matrix is because it sometimes 
appears in texts and I'm confused. If not in the context of OpenGL then 
maybe someone could explain it to me from theoretical point of view.

Besides even if model and view matrices are combined together it doesn't 
mean you cannot extract or define one of them.

So, what a MODEL matrix/transformation is??

BlendMan wrote:
> Andy V wrote:
> 
>> OpenGL does not separate the model and the view matrices -- they are 
>> combined into
>> the single model-view matrix
> 
> 
> I know that. I'm just curious what model matrix is because it sometimes 
> appears in texts and I'm confused. If not in the context of OpenGL then 
> maybe someone could explain it to me from theoretical point of view.
> 
> Besides even if model and view matrices are combined together it doesn't 
> mean you cannot extract or define one of them.
> 
> So, what a MODEL matrix/transformation is??

The model matrix is a tranformation you apply to modelling coordinates to produce world coordinates.

The view matrix is a tranformation you apply to world coordinates to produce eye coordinates.

So, if you want to move one object, adjust its model matrix. If you want
to move the camera around, adjust the view matrix.

--
Andy V

Andy V wrote:
> The model matrix is a tranformation you apply to modelling coordinates 
> to produce world coordinates.
> 
> The view matrix is a tranformation you apply to world coordinates to 
> produce eye coordinates.
> 
> So, if you want to move one object, adjust its model matrix. If you want
> to move the camera around, adjust the view matrix.

OK Andy V, it's clear :)
thanks